1. Field of the Invention
The invention relates to the field of engineering physics, and, in particular, to X-ray scanning for harmful objects or substances located on a human body or hidden in body cavities in order to prevent theft or terrorist acts in buildings, airports, malls, train station, subways and other public places.
2. Description of the Related Art
Human body X-ray scanning for identifying some highly undesirable objects or substances has become critically important in view of terrorist threats. Security applications may include prevention of smuggling of drugs, precious stones and metals, as well as provision of the security at airports, banks, embassies, nuclear power centers and other high-risk locations. X-ray luggage examination in airports is currently the most efficient way to provide the security of the flights. X-ray examination is also used in prisons for visitor's access control.
X-ray luggage examination systems are designed as a conveyer passing through a rectangular frame with an X-ray source installed in the upper part of the frame and a detector of X-radiation installed in the lower part of the frame under the conveyor. However, the described system is not designed for scanning of the passengers due to high level of radiation emitted by an X-ray source, which is used to increase the resolution of the images.
Scanning of passengers for presence of metallic objects hidden under clothing is provided with the help of electromagnetic frames and metal detectors. An X-ray method has not been used until recently for the examination due to its harmful effects on people, especially in cases of frequent use. A number of efforts have been attempted lately to use a low-dose X-ray scanning, which could be applied to examination of people without any threat to their health. One of these systems is X-ray scanning apparatus named Body Search produces by American Science and Engineering, Inc.
A person is scanned with a beam of X-radiation of sufficiently low intensity, while the radiation transmitted through the person's body is converted into an image, which is used to determine the presence of concealed objects. The Body Search system includes housing with an X-ray source of low-intensity, means for shaping an X-ray beam and a detector of X-radiation transmitted through the clothing and reflected by the body. The reflected X-radiation is detected by the detector to generate an image of the objects located on the surface of the body, in the clothing or on the clothing of the portion of the body turned towards the housing with X-ray source.
For full examination it is necessary to make scanning in two positions—i.e., the face towards the housing and the back towards the housing. With this method the internal cavities of the body that are very often used for concealment of drugs and precious stones are not subjected to the examination. Besides, the strongest radiation effects the most sensitive human organs located in the medium portion of the body, while the person's feet and especially shoes that may be used for concealing the contraband are out of the view of the examiner.
Conventional stationary examinations stations employ a single source of low-intensity X-ray radiation. An integrated collimator and a detector of X-ray radiation passed through the body of the person being examined are used. The system also includes a data processing module and a platform for supporting the person being examined. The disadvantage of this system is its stationary nature—it is hard to relocate and calibrate this scanner. Also, such scanners show poor performance for many objects hidden inside body cavities, depending on the angle of orientation of the object and the X-ray beam.
The mobility issue is addressed by an X-ray scanner located in the back of a truck (see EP2458408). An operator workplace and an X-ray scanner system are located in the back of the truck. The system includes a source of X-ray radiation with at least one slit collimator located approximately at a person's navel level. The system also includes a linear detector of X-ray radiation that has passed through the body of the person being examined. The X-ray compartment has two vertical columns with a platform that moves laterally between the columns.
However, the most sensitive body organs located in the middle portion of the body are exposed to the radiation, while legs and, especially, shoes (often used for smuggling objects) are not fully examined by the scanner. Furthermore, the system cannot scan the person's body in a single cycle. Several scans are needed, which reduces the efficiency of the system, because the person has to step onto the platform and remain still during the scan.
Accordingly, there is a need in the art for a safe mobile X-ray scanner system that provides for a complete X-ray scan of person with a high accuracy and improved efficiency.